Constant velocity joints connecting shafts to drive units are common components in automotive vehicles. The drive unit typically has an output shaft or an input shaft for receiving the joint. Typically, the drive unit is an axle, transfer case, transmission, power take-off unit or other torque device, all of which are common components in automotive vehicles. Typically, one or more joints are assembled to the shaft to form a propeller or drive shaft assembly. It is the propeller shaft assembly which is connected, for instance, at one end to the output shaft of a transmission and, at the other end, to the input shaft of a differential. The shaft is solid or tubular with ends adapted to attach the shaft to an inner race of the joint thereby allowing an outer race connection to a drive unit. The inner race of the joint is typically press-fit, splined, or pinned to the shaft making the outer race of the joint available to be bolted or press-fit to a hub connector, flange or stubshaft of the particular drive unit. At the other end of the propeller shaft, the same typical or traditional connection is made to a second drive unit when connecting the shaft between the two drive units. Optionally, the joint may be coupled to a shaft for torque transfer utilizing a direct torque flow connection. Regardless of the connection type, constant velocity joints require, for improved joint life, a sealed environment.
Elastomer boots of the flexible or soft type improve the life of a constant velocity joint by sealing out contaminates and retaining joint lubrication. Elastomer boots are primarily used for sealing two parts that can be articulated relative to one another and which, more particularly, rotate at the same time. These parts constitute a joint. A typical application refers to sealing joints of the constant velocity and universal types. For this purpose, a boot with a cylindrical portion, typically having a smaller diameter is slipped on to a shaft connected to a first joint component, and an annular portion with a greater diameter is connected either directly or via an intermediate element to a second joint component. Between the cylindrical portion and the annular portion with the greater diameter, there extends a wall. The wall has the shape of half a torus for a roll boot, and has a bellows shape for a convoluted boot. When the two joint components articulate relative to one another, the radius of curvature of the wall decreases on the inside of the angle and increases on the outside of the angle. When the joint rotates in the articulated condition, the change in curvature in the roll boot wall moves across the circumference, so that during a complete 360 degree rotation, each point of the boot wall passes through a curvature maximum and a curvature minimum causing flexing of the boot wall. Flexing also occurs for each rotation of the roll boot due to gravitational and centripetal forces. The flexing action may increase material decay caused by mechanical, chemical and thermal attack related to the environment in which the boot is used.
Moreover, a roll boot may be prone to puncture or tearing due to external debris. Additionally, the roll boot may blow out or rupture when subjected to increased lubrication pressure when used in high-speed or high angle joint seal applications.
It would be advantageous to have a boot and sealing system that provides robust performance in most operating conditions indicated above.